Patent application title: Method and device of calculating aircraft braking friction and other relating landing performance parameters based on the data received from aircraft's on board flight data management system

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Abstract:

This invention relates to a method and apparatus for the calculation of
aircraft braking friction and other relating landing parameters,
including but not limited to aircraft braking action, aircraft takeoff
distance, aircraft landing distance, runway surface conditions and runway
surface friction based on the data collected by and available in the
aircraft Flight Data Recorder (FDR) or other flight data management
system, for example, the Quick Access Recorder (QAR), to provide all
involved personnel in the ground operations of an airport and airline
operations, including but not limited to aircraft pilots, airline
operation officers and airline managers as well as airport operators,
managers and maintenance crews, with the most accurate and most recent
information on the true aircraft landing performance parameters to help
better and more accurate safety and economical decision making.

Claims:

1. A computer network for calculating and distributing a true aircraft
friction braking friction coefficient for an aircraft landing surface
comprising: (A) A computer in communication with a flight data management
system of a landing aircraft that is landing or has landed on the
aircraft landing surface, wherein the aircraft's flight data management
system has recorded thereon one or more sets of data points relating to
one or more of the landing aircraft's following flight properties:
aircraft ground speed, aircraft brake pressure, aircraft longitudinal
acceleration, aircraft engine thrust setting, aircraft reverse thrust
setting, aircraft engine revolutions per minute, aircraft air speed,
aircraft vertical acceleration, aircraft spoiler setting, aircraft
airbrake setting, aircraft aileron setting, aircraft flap configuration,
aircraft pitch, and aircraft autobrake setting; (B) Wherein the computer
communicating with the landing aircraft's flight data management system
obtains from the landing aircraft's flight data management system the one
or more sets of the flight property data points recorded on the
aircraft's flight data management system between substantially a point in
time that the landing aircraft touched down on the aircraft landing
surface until a predetermined point in time thereafter; (C) Wherein the
computer communicates with one or more environmental data sources,
wherein the one or more environmental data sources have recorded thereon
one or more sets of data points relating to one or more environmental
parameters, wherein computer obtains from the one or more environmental
data sources the one or more sets of the data points relating to the one
or more environmental parameters chosen from the following group: air
temperature, air pressure, relative humidity, wind speed, wind direction,
pressure altitude, and aircraft landing surface elevation; (D) Wherein
the computer communicates with one or more aircraft data sources, wherein
the one or more aircraft data sources have recorded thereon one or more
sets of data points relating to aircraft parameters pertaining to the
landing aircraft, and wherein the computer obtains from the one or more
aircraft data sources the one or more sets of the data points relating to
aircraft parameters pertaining to the landing aircraft, wherein the one
or more sets of the data points relating to the one or more aircraft
parameters pertaining to the landing aircraft include one or more sets of
the data points relating to one or more aircraft parameters chosen from
the following group: aircraft landing mass, aircraft engine type, number
of aircraft engines, aircraft tire type, and aircraft type; and (E)
Wherein the computer calculates the true aircraft braking friction
coefficient of the aircraft landing surface: (i) using at least one of
the one or more sets of the flight property data points obtained by the
computer from the landing aircraft's flight data management system; (ii)
using at least one of the one or more sets of the data points obtained by
the computer from the one or more environmental data sources; and (iii)
using at least one of the one or more sets of the data points obtained by
the computer from the one or more aircraft data sources.

2. The computer network for calculating and distributing the true
aircraft braking friction coefficient of the aircraft landing surface of
claim 1 wherein the one or more sets of data points relating to one or
more environmental parameters are measured substantially proximate to the
time that the landing aircraft touched down on the aircraft landing
surface.

3. The computer network for calculating and distributing the true
aircraft braking friction coefficient of the aircraft landing surface of
claim 1 wherein the one or more sets of data points relating to one or
more environmental parameters are measured between substantially the
point in time that the landing aircraft touched down on the landing
surface and the predetermined point in time thereafter.

10. The computer network for calculating and distributing the true
aircraft braking friction coefficient of the aircraft landing surface of
claim 1 wherein the one or more sets of the flight property data points
obtained from the landing aircraft's flight data management system are
obtained by the computer in real-time directly or indirectly from the
landing aircraft's flight data management system.

11. The computer network for calculating and distributing the true
aircraft braking friction coefficient of the aircraft landing surface of
claim 1 wherein the one or more sets of the flight property data points
are obtained by the computer directly or indirectly from the landing
aircraft's flight data management system after the landing aircraft
stops.

12. The computer network for calculating and distributing the true
aircraft braking friction coefficient of the aircraft landing surface of
claim 1 wherein the predetermined point in time is after the landing
aircraft substantially reaches taxi speed.

13. The computer network for calculating and distributing the true
aircraft braking friction coefficient of the aircraft landing surface of
claim 1 wherein the predetermined point in time is after the landing
aircraft stops.

14. The computer network for calculating and distributing the true
aircraft braking friction coefficient of the aircraft landing surface of
claim 1 wherein at least one of the one or more environmental data
sources comprises the landing aircraft's flight data management system,
wherein at least one of the one or more sets of the data points relating
to the one or more environmental parameters are measured by
instrumentation on the landing aircraft and are recorded on the landing
aircraft's flight data management system, and wherein at least one of the
one or more sets of the data points relating to the one or more
environmental parameters are obtained from the landing aircraft's flight
data management system by the computer.

15. The computer network for calculating and distributing the true
aircraft braking friction coefficient of the aircraft landing surface of
claim 1 wherein at least one of the one or more aircraft data sources
comprises a computer database, wherein at least one of the one or more
sets of the data points relating to the one or more aircraft parameters
relating to the landing aircraft are recorded on the computer database,
and wherein at least one of the one or more sets of the data points
relating to aircraft parameters pertaining to the landing aircraft are
obtained from the computer database by the computer.

16. The computer network for calculating and distributing the true
aircraft braking friction coefficient of the aircraft landing surface of
claim 1 wherein at least one of the one or more aircraft data sources
comprises the landing aircraft's flight data management system, wherein
at least one of the one or more sets of the data points relating to the
one or more aircraft parameters relating to the landing aircraft are
recorded on the landing aircraft's flight data management system, and
wherein at least one of the one or more sets of the data points relating
to the one or more aircraft parameters are obtained from the landing
aircraft's flight data management system by the computer.

17. The computer network for calculating and distributing the true
aircraft braking friction coefficient of the aircraft landing surface of
claim 1 wherein the aircraft braking friction coefficient calculated by
the computer is distributed by the computer to one or more predetermined
computer output recipients.

18. The computer network for calculating and distributing the true
aircraft braking friction coefficient for the aircraft landing surface of
claim 17 wherein the one or more predetermined computer output recipients
to whom the true aircraft braking coefficient of the aircraft' landing
surface calculated by the computer are distributed are chosen from one or
more of the following groups: airline operation personnel, pilots,
airport personnel, airline managers, airport managers, and airport
maintenance crews.

19. The computer network for calculating and distributing the true
aircraft braking friction coefficient for the aircraft landing surface of
claim 17 wherein the one or more predetermined computer output recipients
to whom the true aircraft braking coefficient of the aircraft landing
surface calculated by the computer are distributed are chosen from one or
more of the following groups: pilots of aircraft scheduled to take off or
land on the aircraft landing surface, personnel involved in ground
operations where the aircraft landing surface is located, aircraft
scheduling and dispatch personnel, flight service center personnel,
government aviation authority personnel, air traffic controllers, airline
employees, and aircraft manufacturers.

Description:

RELATED APPLICATION INFORMATION

[0001] This application is a continuation of co-pending U.S. application
Ser. No. 12/802,065, filed May 28, 2010, which in turn, is a continuation
of U.S. application Ser. No. 11/352,984, filed Feb. 13, 2006, which, in
turn, claims the benefit of and priority from U.S. provisional
application Ser. No. 60/654,914, filed Feb. 23, 2005, all of the
disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of Invention

[0003] This invention relates to the method and the device of calculating
aircraft braking friction and other aircraft performance and pavement
surface characteristics parameters related to aircraft landing and
takeoff including but not limited to aircraft braking action, aircraft
takeoff distance, aircraft landing distance, runway surface conditions
and runway surface friction--from now on referred to as true aircraft
landing performance parameters--based on the data collected or otherwise
available on board of an aircraft in electronic or other format from the
aircraft Flight Data Recorder (FDR) or any other flight data providing or
management system for example the Quick Access Recorder (QAR).

[0004] 2. Background

[0005] Under severe winter conditions airlines, airports, civil aviation
organizations and countries rigorously impose limits on aircraft takeoff,
landing and other surface movement operations as well as enforce weight
penalties for aircraft takeoffs and landings. These limits depend on the
weather, runway and taxiway surface conditions and aircraft braking and
takeoff performance. At the present these limits are calculated from the
assumed aircraft braking performance based on runway conditions. These
conditions are established by visual inspections, weather reports and the
measurements of runway friction coefficient using ground friction
measurement equipment.

[0006] At the present time, there are several practices to calculate the
assumed aircraft braking performance:

[0007] 1. The Canadian CRFI Method:

[0008] The CRFI method comprises a runway surface friction measurement
performed by braking a passenger vehicle traveling on the runway at a
certain speed and measuring the maximum deceleration of it at several
locations along the length of the runway. The measured deceleration data
is taken then and a braking index chart is used to calculate the assumed
aircraft braking performance. The obtained aircraft landing performance
data and calculated assumed braking friction is provided to airline
operators, pilots and airport personnel for decision making.

[0010] There are a great many number of runway friction measurement
devices manufactured by different companies, in different countries and
working based on different principles. Some of the most common devices
are: (a) continuous friction measurement equipment (CFME); (b)
decelerometers; and (c) side force friction coefficient measurement
equipment. This equipment is operated by airport operation personnel
according to the manufacturer's instructions on the runways, aprons, and
taxiways and the measured friction coefficient is recorded. The recorded
friction coefficient is then distributed to airline operation personnel,
pilots, and airport personnel. The measured coefficient of friction is
dependent on the measurement device. Under the same conditions and on the
same runway different runway friction measurement devices based on
different principles will record different runway friction coefficients.
These runway friction coefficients are assumed to relate to actual
aircraft landing and takeoff performance.

[0011] 3. The New Proposed IRFI Method:

[0012] The International Runway Friction Index (IRFI) is a computational
method to harmonize the reported runway friction numbers reported by the
many different runway surface friction measurement equipments. The method
was developed through an international effort with 14 participating
countries. The method is a mathematical procedure based on simple linear
correlations. The IRFI procedure is using a mathematical transformation
to take the reported measurement of a runway friction measurement device
and compute using simple mathematical methods an index called the IRFI.
The mathematical procedures are the same for all the different runway
friction measurement device using a different set of constant parameters
that was determined for each individual device. It is assumed that using
this procedure the different runway friction measurement devices
reporting different friction coefficients can be harmonized. The
calculated IRFI is assumed to correlate to aircraft landing and takeoff
performance.

[0014] This method is available for airport operators according to new
regulations. The method is based on airport personnel driving through the
runway and personally observing the runway surface conditions. The ice,
snow, water and other possible surface contaminants are visually observed
and their depth measured or estimated by visual observation. The
estimated runway conditions with weather information are then used to
lookup runway friction coefficient in a table.

[0015] All these above mentioned practices are based on the measurement of
the runway friction coefficient using ground friction measuring
equipment, visual observation, weather information or combinations of
these. However, according to present practices, there are several
problems with the measurement of the runway friction coefficient using
these methods.

[0016] 1. Need of a Special Device/Car:

[0017] There is a special car needed to be able to measure the runway
friction coefficient. There are special devices to measure the runway
friction coefficient that are commercially available; however, most of
these devices are very expensive. Therefore, not every airport can afford
to have one.

[0018] 2. Close of Runway:

[0019] For the duration of the measurement the runway has to be closed for
takeoffs and landings as well as any aircraft movement. The measurement
of the runway surface friction takes a relatively large amount of time
since a measuring device has to travel the whole length of the runway at
a minimum one time but during severe weather conditions it is possible
that more than one measurement run is needed to determine runway surface
friction. The closing of an active runway causes the suspension of
takeoff and landing aircraft operations for a lengthened period of time
and therefore is very costly for both the airlines and the airport. The
use of ground vehicles to measure runway friction poses a safety hazard
especially under severe weather conditions.

[0020] 3. Inaccurate Result Due to Lack of Maintenance and Inaccurate
Calibration Level:

[0021] The result of the measurements are very dependent of the
maintenance and the calibration level of measurement devices, therefore
the result can vary much, and could lose reliability.

[0022] 4. Confusing Results Due to the Differences Between Ground Friction
Devices:

[0023] It has been established that the frictional values reported by
different types of ground friction measurement equipment are
substantially different. In fact, the same type and manufacture, and even
the same model of equipment frequently report highly scattered frictional
data. Calibration and measurement procedures are different for different
types of devices. The repeatability and reproducibility scatter, or in
other words, uncertainty of measurements for each type of ground friction
measurement device, is therefore amplified and the spread of friction
measurement values among different equipment types is significant.

[0024] 5. Inaccurate Result Due to Rapid Weather Change:

[0025] Airport operation personnel, in taking on the responsibility of
conducting friction measurements during winter storms, find it difficult
to keep up with the rapid changes in the weather. During winter storms
runway surface conditions can change very quickly and therefore friction
measurement results can become obsolete in a short amount of time, thus
misrepresenting landing and takeoff conditions.

[0026] 6. Inaccurate Result Due to the Difference Between Aircraft and the
Ground Equipment:

[0027] It is proven that the aircraft braking friction coefficients of
contaminated runways are different for aircrafts compared to those
reported by the ground friction measurement equipment.

[0028] 7. Inaccurate Result Due to the Lack of Uniform Runway Reporting
Practices:

[0029] For many years the international aviation community has had no
uniform runway friction reporting practices. The equipment used and
procedures followed in taking friction measurements vary from country to
country. Therefore, friction readings at various airports because of
differences in reporting practices may not be reliable enough to
calculate aircraft braking performance.

[0030] Therefore this invention recognizes the need for a system directly
capable of determining the true aircraft landing performance parameters
based on the data collected by and available in the aircraft Flight Data
Recorder (FDR) or other flight data management systems. By utilizing the
novel method in this invention, for the first time all involved personnel
in the ground operations of an airport and airline operations including
but not limited to aircraft pilots, airline operation officers and
airline managers as well as airport operators, managers and maintenance
crews, will have the most accurate and most recent information on runway
surface friction and aircraft braking action, especially on winter
contaminated and slippery runways.

[0031] Utilizing this method the aviation industry no longer has to rely
on different friction reading from different instrumentations and from
different procedures.

[0032] Therefore, this method will represent a direct and substantial
benefit for the aviation industry.

BRIEF SUMMARY OF THE INVENTION

Objective of Invention

[0033] The objective of this invention is to provide all personnel
involved in the ground operations of an airport and involved in airline
operations including but not limited to aircraft pilots, airline
operation officers and airline managers as well as airport operators,
managers and maintenance crews, the most accurate and most recent
information on the true aircraft landing and takeoff performance
parameters to help in a better and more accurate safety and economical
decision making, and to prevent any accident, therefore save lives.

Brief Summary of the Invention

[0034] This unique and novel invention is based on the fact that most
modern airplanes throughout the entire flight including the takeoff and
landing measures, collects and stores data on all substantial aircraft
systems including the braking hydraulics, speeds and hundreds of other
performance parameters. During the landing maneuver real time or after
the aircraft parked at the gate this data can be retrieved, processed and
the true aircraft landing performance parameters can be calculated.

[0035] During a landing usually an aircraft uses its speed brakes,
spoilers, flaps and hydraulic and mechanical braking system and other
means to decelerate the aircraft to acceptable ground taxi speed. The
performance of these systems together with many physical parameters
including but not limited to various speeds, deceleration, temperatures,
pressures, winds and other physical parameters are monitored, measured,
collected and stored in a data management system on board of the aircraft
(FIG. 1).

[0036] All monitored parameters can be fed real time into a high powered
computer system that is capable of processing the data and calculating
all relevant physical processes involved in the aircraft landing
maneuver. Based upon the calculated physical processes the actual
effective braking friction coefficient of the landing aircraft can be
calculated. This, together with other parameters and weather data, can be
used to calculate the true aircraft landing performance parameters (FIG.
6).

[0037] If real time data processing is not chosen, then the collected data
from the aircraft can be transported by wired, wireless or any other
means into a central processing unit where the same calculation can be
performed (FIG. 8).

[0038] The obtained true aircraft landing performance parameters data then
can be distributed to all involved personnel in the ground operations of
an airport and airline operations including but not limited to aircraft
pilots, airline operation officers and airline managers as well as
airport operators, managers and maintenance crews.

[0039] Utilizing the novel method in this invention for the first time all
personnel involved in the ground operations of an airport and airline
operations including but not limited to aircraft pilots, airline
operation officers and airline managers as well as airport operators,
managers and maintenance crews, will have the most accurate and most
recent information on runway surface friction and aircraft braking
action.

[0040] Utilizing this method, all the above mentioned (see BACKGROUND OF
THE INVENTION) problems can be solved:

[0041] 1. No Need of a Special Device/Car:

[0042] This method uses the airplane itself as measuring equipment,
therefore no additional equipment is needed. Moreover, no additional
sensor is needed. This method uses the readings of present sensors and
other readily available data of an aircraft.

[0043] 2. No Need for Closing of Runway:

[0044] The duration of the measurement is the landing of the aircraft
itself. Therefore the runway does not have to be closed.

[0045] 3. No Inaccurate Result Due to Maintenance and the Calibration
Level:

[0046] Because this method uses the aircraft itself as the measuring
device, there is no variation due to the maintenance and the calibration
level of these ground friction measuring devices. The result of the
calculation will give back the exact aircraft braking friction the
aircraft actually develops and encounters.

[0047] 4. No Inaccurate Result Due to the Different Between Ground
Friction Devices:

[0048] Because this method uses the aircraft itself as the measuring
device, there is no variation due to the different ground friction
measuring devices.

[0049] 5. Accurate Result Even in Rapid Weather Change:

[0050] As long as aircraft are landing on the runway, the most accurate
and most recent information on the true aircraft landing performance
parameters will be provided by each landing.

[0051] 6. No Inaccurate Result Due to the Difference Between Aircraft and
the Ground Equipment:

[0052] Because this method uses the aircraft itself as the measuring
device, there is no discrepancy in the measured and real friction due to
the difference between aircraft and the ground equipment.

[0053] 7. No Inaccurate Result Due to the Lack of Uniform Runway Reporting
Practices:

[0054] Because this method uses the aircraft itself as the measuring
device, there is no variation due to the difference in reporting
practices.

[0055] Utilizing this method the aviation industry no longer has to rely
on different friction readings from different instrumentations and from
different procedures.

[0056] Therefore, this method represents a direct and substantial safety
and economic benefits for the aviation industry.

[0057] The significance of this invention involves saving substantial
amount of money for the airline industry by preventing over usage of
critical parts and components of the aircraft, including but not limited
to brakes, hydraulics, and engines.

[0058] While increasing the safety level of the takeoffs, it could
generate substantial revue for airlines by calculating the allowable take
off weight, thus permissible cargo much more precisely.

BRIEF DESCRIPTION OF THE DRAWINGS

[0059]FIG. 1 is a schematic of a Flight Data Recorder illustrating the
data collection structure of the Flight Data Recorder of an aircraft.

[0060]FIG. 2 is a table illustrating data available from the Flight Data
Recorder of a landing aircraft to reflect Pressure Altitude (in feet)
versus time during a landing of the aircraft.

[0061]FIG. 3 is a table illustrating data available from the Flight Data
Recorder of a landing aircraft to reflect Brake Pressure (in pounds per
square inch) versus Time during or landing of the aircraft.

[0062] FIG. 4 is a table illustrating data available from the Flight Data
Recorder of a landing aircraft to reflect Autobrake Setting versus Time
during landing of the aircraft.

[0063] FIG. 5 is a table illustrating a fraction of data available from a
Flight Data Recorder.

[0064]FIG. 6 is a schematic flow chart illustrating the method of
determining various values generated by the present invention.

[0066]FIG. 8 is a schematic illustrating transmission of data from a
Flight Data Management System of a landing aircraft for post processing
and distribution.

[0067]FIG. 9 is a schematic illustrating alternative real-time post
processing and distribution and transmission of data from a Flight Data
Management System of a landing aircraft.

DETAILED DESCRIPTION OF THE INVENTION

[0068] As illustrated in FIG. 1, this unique and novel invention is based
on the fact that every airplane during landing uses the hydraulics and
braking system. During a landing usually an aircraft uses its speed
brakes, spoilers, flaps and hydraulic and mechanic braking system and
other means to decelerate the aircraft to acceptable ground taxi speed.
The performance of these systems together with many physical parameters
including but not limited to various speeds, deceleration, temperatures,
pressures, winds and other physical parameters are monitored, measured,
collected and stored in a data management system on board of the
aircraft. This figure presents the schematics of the three major
components of data sources onboard of an aircraft relevant to this
invention, the measured and recorded parameters related to the braking
system, the measured and recorded parameters to the engines, flight and
other control systems of the aircraft, and the dynamic, external and
environmental parameters measured and recorded.

[0069] As illustrated in FIGS. 2 through 5, this invention uses the
sequence of data points recorded from the touch down of the aircraft
until it reaches the normal taxiing speed or comes to a stop. In the
continuous data stream of the flight data management system the touch
down is marked by several events making it possible to detect the
beginning data point of the calculation process. From that point until
the aircraft comes to complete stop at the gate every necessary data
points can be identified within the recorded data. FIG. 2 shows the
recorded altitude measurements for an actual landing FIG. 3 depicts the
measured the recorded hydraulic braking pressures, FIG. 4 presents the
recorded data for the auto-brake selection and FIG. 5 illustrate the
format of the recorded data that can be obtained form a digital flight
data management system.

[0070] As illustrated in FIG. 6, to arrive at the end result, a number of
different mathematical and physical modeling approaches are possible
through different sets of dynamic equations and/or various methods of
simulations based upon the availability of different sets of data from
the flight data management system.

[0071] The following equations only represent an example of the possible
approaches, and therefore the invention and the presented method is not
limited to these equations.

[0072] 6.1--The following data is used as one of the possible minimum data
sets for the calculation, although more and/or different data can be
utilized to calculate the same parameters and/or improve the precision of
the calculation.

[0099] 6.2--The method calculates, through a three-dimensional dynamic
model, all relevant physical processes involved in the aircraft landing
maneuver and separates them so they are individually available for use.
The first intermediate result of the method is the time or distance
history of all relevant, separated, interdependent decelerations
generated by the different systems in an aircraft. These decelerations
are cumulatively measured by the onboard measurement system and reported
in the flight data stream. The separated decelerations calculated from
the different physical processes make it possible to calculate the true
deceleration developed only by the actual effective braking friction
coefficient of the landing aircraft.

[0100] Based on the above, the software calculates the brake effective
acceleration vs. time based on Equation (1).

ABe=Ax-ADrag-A.sub.ReverseThrust-A.sub.RollingResistance--
APitch (1)

[0101] where ABe is the brake effective acceleration [0102] Ax
is the measured cumulative longitudinal acceleration (6.1) [0103]
Apreg is the deceleration due to the aerodynamic drag,

[0103] ADrag=f(V.sub.air,S.sub.spoiler,S.sub.airbrake,Saileron-
`,C.sub.flap,T.sub.air,P.sub.air,H.sub.%,Mlanding,TYaircraft)
(2) [0104] where
V.sub.air,S.sub.spoiler,S.sub.airbrake,Saileron,C.sub.flap,T.sub.air-
,P.sub.air,H.sub.%,Mlanding,TYaircraft are parameters from 6.1.
[0105] A.sub.ReverseThrust is the acceleration caused by
thrust/reverse-thrust

[0105] A.sub.ReverseThrust=f(E.sub.type,N.sub.engine,T.sub.air,P.sub.air-
,H.sub.%,E.sub.RPM,SRT,Mlanding,TYaircraft) (3)
[0106] where
E.sub.type,N.sub.engine,T.sub.air,P.sub.air,H.sub.%,E.sub.RPM,SRT,M.-
sub.landing;TYaircraft are parameters from 6.1 [0107]
A.sub.RollingResistance is the cumulative deceleration due to other
effects such as tire rolling resistance, runway longitudinal elevation

[0107] A.sub.RollingResistance=f(tire,Vg,Mlanding) (4)
[0108] where tire,Vg,Mlanding are parameters from 6.1 [0109]
Apitch is due to the runway elevation

[0109] APitch=f(ΔRunway) (5) [0110] where
ΔRunway is the runway elevation from 6.1.

[0111] This true deceleration (ABe) developed only by the actual
effective braking friction coefficient of the landing aircraft, then can
be used in further calculations to determine the true aircraft braking
coefficient of friction.

[0112] 6.3--Using the recorded data stream of the aircraft with the
parameters indicated in point 6.1, plus weather and environmental factors
reported by the airport or measured onboard of the aircraft and therefore
available in the recorded data, together with known performance and
design parameters of the aircraft available from design documentation and
in the literature, the dynamic model calculates all relevant actual
forces acting on the aircraft as a function of the true ground and air
speeds, travel distance and time. Using the results, the dynamic wheel
loads of all main gears and the nose gear can be calculated.

[0113] Since the dynamic vertical acceleration of the aircraft is measured
by the onboard inertial instrumentation, the effective dynamic wheel load
(N) can be calculated by the deduction of the calculated retarding forces
by means of known aircraft mass; together with the determined
gravitational measurement biases introduced by runway geometry and
aircraft physics using Equations 6 through 9.

[0114] Where [0115] Lift is the computed force of the sum of all lifting
forces acting on the aircraft through aerodynamics:

[0115] Lift=f(V.sub.air,S.sub.spoiler,S.sub.airbrake,Saileron,C.sub-
.flap,T.sub.air,P.sub.air,H.sub.%,Mlanding,TYaircraft) (7)
[0116] where
V.sub.air,S.sub.spoiler,S.sub.airbake,Saileron,C.sub.flap,T.sub.air,-
P.sub.air,H.sub.%,Mlanding,TYaircraft are parameters from point
6.1. [0117] LoadTransfer is the load transfer from the main landing
gear to the nose gear due to the deceleration of the aircraft:

[0117] LoadTransfer=f(ABe,Mlanding,TYaircraft) (8)
[0118] where ABe,Alanding,TYaircraft are parameters from
6.1. [0119] MomentumLift is the generated loading or lifting forces
produced by moments acting on the aircraft body due to the acting points
of lift, thrust and reverse-thrust forces on the aircraft geometry:

[0119] MomentumLift=f(SThrust,SRT,C.sub.flap,TYaircraft)
(9) [0120] where SThrust,SRT,C.sub.flap,TYaircraft
are parameters from point 6.1 [0121] g(Ac,Mlanding) is the
dynamic force acting on the landing gear due to the dynamic vertical
movement of the aircraft, and thus the varying load on the main gear due
to the runway roughness, [0122] where Ac,Mlanding are
parameters from point 6.1.

[0123] 6.4--The deceleration caused by the wheel braking system of the
aircraft calculated in point 6.2 (ABe is the true brake effective
deceleration), together with the computed actual wheel load forces acting
on the main gears of the aircraft can be used to calculate the true
braking coefficient of friction. First the actual true deceleration force
or friction force (FFr) caused by the effective braking of the
aircraft have to be computed. From the brake effective deceleration
(ABe) obtained in 6.2 and the available aircraft mass, the method
calculates the true effective friction force based on the formula:

FFr=MlandingABe (10)

[0124] where Mlanding is the landing mass of the aircraft from point
6.1 and [0125] ABe is the calculated brake effective deceleration
from Equation (1).

[0126] The determined true deceleration force (FFr) in equation 10
together with the actual effective dynamic wheel load (N) obtained in 6.3
can be utilized to calculate the true effective braking coefficient of
friction μ using equation 11:

μ=FFr/N (11)

[0127] where [0128] N is the calculated effective dynamic wheel force
acting on the tire (6.3), [0129] and FFr is the friction force from
Equation (10).

[0130] 6.5--Using the calculated effective true frictional forces,
together with parameters measured by the aircraft data management system
(such as downstream hydraulic braking pressure), a logical algorithm
based on the physics of the braking of pneumatic tires with antiskid
braking systems was designed to determine whether the maximum available
runway friction was reached within the relevant speed ranges of the
landing maneuver.

[0131] Together with the actual friction force the following logic is used
by this invention to determine:

[0132] (A) If friction limited braking is encountered--If the actual
available maximum braking friction available for the aircraft was reached
by the braking system and even though more retardation was needed the
braking system could not generate because of the insufficient amount of
runway surface friction a friction limited braking was encountered.

[0133] (B) If adequate friction for the braking maneuver was available--If
friction limited braking was not encountered and the braking was limited
by manual braking or the preset level of the auto-brake system, the
adequate surface friction and actual friction coefficient can be
calculated and verified.

[0134] 6.6--In order to make sure that the auto-brake and antiskid systems
of the aircraft were working in their operational range, the algorithm
analyzes the data to look for the friction limited sections only in an
operational window where the landing speed is between 20 m/s and 60 m/s.

[0135] 6.7--From the computed true effective braking coefficient of
friction μ calculated in 6.4, the method computes the theoretically
necessary hydraulic brake pressure Pbrake and from the dynamics of
the landing parameters an applicable tolerance is calculated t.

[0136] 6.8--The data is analyzed for the deviation of the applied
downstream hydraulic brake pressure from the calculated theoretical brake
pressure from 6.7 according to the obtained effective braking friction
within the allowed operational window by the determined t tolerance. A
sharp deviation of the achieved and the calculated hydraulic braking
pressure is the indication of friction limited braking. When sharply
increased hydraulic pressure is applied by the braking system, while no
significant friction increase is generated, the potential of true
friction limited braking occurs.

[0137] FIG. 7 illustrates a graphical presentation for an example for the
friction limited braking, where it can be seen that that a sharply
increasing hydraulic pressure is applied by the braking system, while the
friction is decreasing. This is a very good example for a true friction
limited braking.

The Different Applications of this Method

The Post Processing

[0138]FIG. 8 illustrates one possible approach in obtaining the true
aircraft landing performance parameters is a method of post processing.
The data from the aircraft flight data management system is retrieved not
real time but only after the aircraft is finished its landing, taxiing
and other ground maneuvers and arrived at its final ground position. The
schematic of this approach is described in FIG. 8.

[0139] 8.1--All monitored and available data is sent to the flight data
management system throughout the aircraft landing and ground maneuver.

[0140] 8.2--The Flight Data Management system collects, processes and
stores the retrieved data in a data storage. The data storage is in fact
part of the Flight Data Management system where all the data is stored.

[0141] 8.3--Data transfer--After the airplane stopped at the gate or other
designated final position, the collected data from the aircraft can be
transported by wired, wireless or other means into a central processing
unit.

[0142] 8.4--High Power computer--All recorded parameters transported from
the aircraft can be fed into a computer system, which is capable of
processing the data and calculating/simulating all relevant physical
processes involved in the aircraft landing maneuver and the actual
effective braking friction coefficient of the landing aircraft and the
true aircraft landing performance parameters can be computed and made
ready for distribution.

[0144] As illustrated in FIG. 9, in the case of real time data processing,
all monitored parameters can be fed real time into an onboard high power
computer system that is capable of processing the data and calculating
all relevant physical processes involved in the aircraft landing
maneuver. Based upon the calculated physical processes the actual
effective braking friction coefficient of the landing aircraft can be
calculated. This together with other parameters and weather data can be
used to calculate the true aircraft landing performance parameters. In
case the calculation finds a true friction limited section, a warning can
be sent to the pilot to prevent any accident, such as over run or slide
off the runway.

[0145] 9.1--All monitored and available data is sent to the flight data
management system throughout the aircraft landing and ground maneuver.

[0146] 9.2--The Flight Data Management system collects, processes and
stores the retrieved data in a data storage. The data storage is in fact
part of the Flight Data Management system where all the data is stored.

[0147] 9.3--High power computer system: All monitored parameters are fed
real time into a computer system, which is capable of processing the data
and calculating/simulating all relevant physical processes involved in
the aircraft landing maneuver and the actual effective braking friction
coefficient of the landing aircraft and the true aircraft landing
performance parameters.

[0148] 9.4--Pilot warning: Based on the calculated aircraft braking
coefficient and the method to search for friction limited braking it
gives a warning in case the friction is too low or continuously informs
the driver of the generated and available braking and cornering
coefficient of friction.

[0150] Utilizing the novel method in this invention for the first time all
personnel involved in the ground operations of an airport as well as
airline personnel involved in operations including but not limited to
aircraft pilots, airline operation officers and airline managers as well
as airport operators, managers and maintenance crews, will have the most
accurate and most recent information on runway surface friction and
aircraft braking action.

[0151] Utilizing this method the aviation industry no longer has to rely
on different friction readings from different instrumentations and from
different procedures or assumed friction levels based on visual
observation and weather data

[0152] Therefore, this method represents a direct and substantial safety
and economic benefits for the aviation industry.

Economic Benefits

[0153] The significance of this invention involves knowing the true
aircraft landing performance parameters for landing which yields
substantial financial savings for the airline industry. While increasing
the safety level of the takeoffs, it could also generate substantial
revenue for airlines.

[0154] Therefore a system directly capable of determining the true
aircraft landing performance parameters would represent direct and
substantial economic benefit for the aviation industry including but not
limited to: [0155] 1. Preventing over usage of critical parts,
components of the aircraft including but not limited to brakes,
hydraulics, and engines. [0156] 2. The distribution of the calculated
parameters for the airport management helps make more accurate, timely
and economic decisions including but not limited to decision on closing
the airport or decision on the necessary maintenance. [0157] 3. The
calculated parameters reported to the airline management yields more
accurate and economic decision making including but not limited to
permitting the calculation of allowable take off weights much more
precisely thus increasing the permissible cargo limits

Safety Benefits

[0158] The significance of this invention involves the precise assessment
of the true runway surface characteristics and aircraft braking and
landing performance by providing the true aircraft landing performance
parameters. This is fundamental to airport aviation safety, and
economical operations especially under winter conditions and slippery
runways. Thus, a system directly capable of determining the true aircraft
landing performance parameters real-time and under any conditions without
restricting ground operations of an airport would represent direct and
substantial safety benefit for the aviation industry including but not
limited to: [0159] 1. Providing real-time low friction warning to help
pilots to make critical decisions during landing or take-off operations
to prevent accidents, costly damages or loss of human lives. [0160] 2.
Eliminating the confusion in the interpretation of the different Ground
Friction Measuring Device readings and therefore giving precise data to
airport personnel for critical and economical decision making in airport
operations and maintenance. [0161] 3. Giving an accurate assessment of
the actual surface conditions of the runway, that could be used in the
aircraft cargo's loading decision making for safer landing or take-offs.
[0162] 4. Providing accurate data for distribution to airport management
personnel assisting them in more accurate, timely and safe decision
making. [0163] 5. Providing data to be reported to pilots about to land
for safer and more accurate landing preparation. [0164] 6. Providing data
to be reported to pilots about to take off for safer and more accurate
takeoff preparation. [0165] 7. It could be reported to the airline
management to for more accurate safety decision making.

Patent applications by Zoltán Iván Radó, Budapest HU

Patent applications in class Having coefficient of friction or road condition determining means

Patent applications in all subclasses Having coefficient of friction or road condition determining means